Goals
Understand what some and every do
Write your own version of some and every
some
Iterates through an array
Runs a callback on each value in the array
If the callback returns true for at least one single value, return true
Otherwise, return false
the result of the callback will always be a boolean
An Example
let numbers = [1,2,3];
numbers.some(function(value, index, array){
return value < 3;
});
// true
let numbers = [1,2,3];
numbers.some(function(value, index, array){
return value > 10;
});
// false
JavaScript
How Does It Work?
function some(array, callback){
for(let i = 0; i < array.length; i++){
if(callback(array[i], i, array) === true){
return true;
}
}
return false;
}
JavaScript
Iterates through an array
Runs a callback on each value in the array
If the callback returns true for at least one single value, return true
Otherwise, return false
Using Some In A Function
function hasAdmin(arr){
return arr.some(function(value){
return value.admin
});
}
hasAdmin([
{name: "Colt", admin: true},
{name: "Poppy", admin: false}
]); // true
hasAdmin([{name: "Colt"}, {name: "Poppy", admin: false}]); // false
JavaScript
function hasQuestionMark(str){
return str.split('').some(function(value){
return value === '?';
});
}
hasQuestionMark('How are you feeling'); // false
hasQuestionMark('How are you feeling now?'); // true
JavaScript
When You Would Use Some
You need to determine if at least one value in an array exists and you have to determine this by using a callback (not includes/indexOf)
A simple alternative to using filter and seeing if the array contains at least one element
every
Iterates through an array
Runs a callback on each value in the array
If the callback returns false for any single value, return false
Otherwise, return true
the result of the callback will always be a boolean
An Example
let numbers = [1,2,3];
numbers.every(function(value, index, array){
return value > 0;
});
// true
let numbers = [1,2,3];
numbers.every(function(value, index, array){
return value > 2;
});
// false
JavaScript
How Does It Work?
Iterates through an array
Runs a callback on each value in the array
If the callback returns false for any single value, return false
Otherwise, return true
function every(array, callback){
for(let i = 0; i < array.length; i++){
if(callback(array[i], i, array) === false){
return false;
}
}
return true;
}
JavaScript
Using Every In A Function
function allVowels(str){
return str.split('').every(function(value){
return "aeiou".includes(value)
});
}
allVowels('awesome')// falseallVowels('aiaieoeoiu')// truefunction allIntegers(arr){
return arr.every(Number.isInteger);
}
allIntegers([1,2,3,4,4,4,4])// trueallIntegers([5,1,4,3,2.2])// false
JavaScript
When You Would Use Every
You need to determine if every value in an array exists and you have to determine this by using a callback
A simple alternative to using filter and seeing if the filtered array is of the same length as the original array
Recap
some iterates through an array and runs a callback on each value,
if the callback for at least one value returns true, some returns true, otherwise false
every iterates through an array and runs a callback on each value,
if the callback at any time returns false, every returns false